1. Field of the Invention
The present invention relates to a photosensitive resin composition, a pattern forming method and electronic parts using the photosensitive resin composition. More particularly, the present invention relates to a photosensitive resin composition used for substrates for forming various mounting circuits and circuit substrates, and especially substrates for forming the circuit and circuit substrate as parts for forming an electric signal line directly on a suspension for a hard disc drive whose high capacity and downsizing are rapidly required, and a pattern forming method and electronic parts using the photosensitive resin composition.
2. Description of the Related Art
In terms of making high storage capacity and realizing speeding up in a hard disc drive, in place of a conventional MIG (metal in gap) or a magnetic induction type thin film as a magnetic head, a so-called MR (magneto resistive)-thin film hybrid type head obtained by integrating a magneto resistive type MR element with a thin film has been noticed.
Reading and writing of a magnetic signal are divided in one head in the MR head whereas the reading and writing are performed together in one head in the conventional head. Thus, a number of terminals are doubled (ground terminals are added as needed), and it becomes necessary to make a wire connecting the head to the disc main body a thin line.
However, when the line is made thin, the wire is easily corroded, impedances are hardly integrated, and mounting of the head becomes difficult. As a method for solving such a new problem, the method for forming the circuit directly on the suspension to which the head is mounted has been proposed by, for example Japanese Patent Application Laid-Open No. 48-16620-A.
A polyimide resin layer having and combining excellent resistance to heat, electric property and mechanical property is used for the above substrate for forming the circuit. However, when the polyimide resin layer has a high water absorption and such a substrate for forming the circuit is incorporated as the suspension in the hard disc drive main body, a dimension is largely altered as the water is absorbed in the polyimide resin layer, then the suspension itself is warped, and alignment accuracy is reduced as well as a distance between the disc and the main body is changed to cause performance fault as the device.
The polyimide resin having the low water absorption often contains fluorine, and is inflexible in structure. Thus, when such a polyimide resin is made photosensitive, its solubility in an organic solvent as a developing solution becomes remarkably low, and the development becomes difficult.
The present invention has been made in order to solve the conventional problems as the above, and an object of the present invention is to provide a photosensitive resin composition having a low water absorption and a good solubility in a developing solution and capable of forming a good pattern, as well as a pattern forming method and electronic parts using the photosensitive resin composition.